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[dev.typeparams] go/types: "comparable" must not be visible before Go 1.18

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This is a straightforward port of CL 331517 to go/types.

Change-Id: Id00761fd5dffb4d09e19f086d18ddc20f11528d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/335032
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Rob Findley 2021-07-16 09:44:08 -04:00 committed by Robert Findley
parent 79955155e9
commit 726ffce659
3 changed files with 32 additions and 43 deletions
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9
src/go/types/testdata/fixedbugs/issue46090.go2 vendored Normal file
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@ -0,0 +1,9 @@
// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// The predeclared type comparable is not visible before Go 1.18.
package go1_17
type _ comparable // ERROR undeclared

2
src/go/types/typexpr.go
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@ -27,7 +27,7 @@ func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, wantType bool)
// Note that we cannot use check.lookup here because the returned scope
// may be different from obj.Parent(). See also Scope.LookupParent doc.
scope, obj := check.scope.LookupParent(e.Name, check.pos)
if obj == nil {
if obj == nil || obj == universeComparable && !check.allowVersion(check.pkg, 1, 18) {
if e.Name == "_" {
check.errorf(e, _InvalidBlank, "cannot use _ as value or type")
} else {

54
src/go/types/universe.go
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@ -8,7 +8,6 @@ package types
import (
"go/constant"
"go/internal/typeparams"
"go/token"
"strings"
)
@ -27,6 +26,7 @@ var (
universeRune *Basic // int32 alias, but has name "rune"
universeAny *Interface
universeError *Named
universeComparable Object
)
// Typ contains the predeclared *Basic types indexed by their
@ -79,21 +79,30 @@ func defPredeclaredTypes() {
def(NewTypeName(token.NoPos, nil, t.name, t))
}
// any
// (Predeclared and entered into universe scope so we do all the
// usual checks; but removed again from scope later since it's
// only visible as constraint in a type parameter list.)
// type any = interface{}
// Entered into universe scope so we do all the usual checks;
// but removed again from scope later since it's only visible
// as constraint in a type parameter list.
def(NewTypeName(token.NoPos, nil, "any", &emptyInterface))
// Error has a nil package in its qualified name since it is in no package
// type error interface{ Error() string }
{
res := NewVar(token.NoPos, nil, "", Typ[String])
sig := &Signature{results: NewTuple(res)}
sig := NewSignature(nil, nil, NewTuple(res), false)
err := NewFunc(token.NoPos, nil, "Error", sig)
typ := &Named{underlying: NewInterfaceType([]*Func{err}, nil)}
sig.recv = NewVar(token.NoPos, nil, "", typ)
def(NewTypeName(token.NoPos, nil, "error", typ))
}
// type comparable interface{ ==() }
{
sig := NewSignature(nil, nil, nil, false)
eql := NewFunc(token.NoPos, nil, "==", sig)
typ := &Named{underlying: NewInterfaceType([]*Func{eql}, nil)}
sig.recv = NewVar(token.NoPos, nil, "", typ)
def(NewTypeName(token.NoPos, nil, "comparable", typ))
}
}
var predeclaredConsts = [...]struct {
@ -202,33 +211,6 @@ func DefPredeclaredTestFuncs() {
def(newBuiltin(_Trace))
}
func defPredeclaredComparable() {
// The "comparable" interface can be imagined as defined like
//
// type comparable interface {
// == () untyped bool
// != () untyped bool
// }
//
// == and != cannot be user-declared but we can declare
// a magic method == and check for its presence when needed.
// Define interface { == () }. We don't care about the signature
// for == so leave it empty except for the receiver, which is
// set up later to match the usual interface method assumptions.
sig := new(Signature)
eql := NewFunc(token.NoPos, nil, "==", sig)
iface := NewInterfaceType([]*Func{eql}, nil)
// set up the defined type for the interface
obj := NewTypeName(token.NoPos, nil, "comparable", nil)
named := NewNamed(obj, iface, nil)
obj.color_ = black
sig.recv = NewVar(token.NoPos, nil, "", named) // complete == signature
def(obj)
}
func init() {
Universe = NewScope(nil, token.NoPos, token.NoPos, "universe")
Unsafe = NewPackage("unsafe", "unsafe")
@ -238,15 +220,13 @@ func init() {
defPredeclaredConsts()
defPredeclaredNil()
defPredeclaredFuncs()
if typeparams.Enabled {
defPredeclaredComparable()
}
universeIota = Universe.Lookup("iota").(*Const)
universeByte = Universe.Lookup("byte").(*TypeName).typ.(*Basic)
universeRune = Universe.Lookup("rune").(*TypeName).typ.(*Basic)
universeAny = Universe.Lookup("any").(*TypeName).typ.(*Interface)
universeError = Universe.Lookup("error").(*TypeName).typ.(*Named)
universeComparable = Universe.Lookup("comparable")
// "any" is only visible as constraint in a type parameter list
delete(Universe.elems, "any")